water temp senders..

i have a gti 1800 and on the front of the block there is the metal housing that holds 2 water temp switchs on mine it has a one pin one that a spade terminal clips onto. and also has a massive one prob about a 22mm spanner size to undo with a double pin on the top and the colour is brown.
what is it for? also anyone got a part numbr for the both of them and the metal housing?

thanking you!
happy xmas and new year!!

One's the thermo time switch.

take it thats the 2pin brown one then as the other 1pin little thing is for the temp gauge.
chears